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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Object-Oriented style question
Date: Tue, 10 Jan 2012 09:34:22 +0100
Organization: cbb software GmbH
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Date: 2012-01-10T09:34:22+01:00
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On Mon, 9 Jan 2012 14:34:17 -0800 (PST), Adam Beneschan wrote:

> I think there are very good reasons for using anonymous access-
> subprogram parameters.

No. In most cases access-to-subprogram parameter should have been a
subprogram parameter, if Ada only supported that.

If you meant rather that anonymous access to subprogram is better than
named one, that is also debatable. Anonymous access-to-subprogram is weakly
typed in the sense that it wrongly presumes that all subprograms of same
parameter profile are exchangeable = belong to compatible subtypes.

That is certainly not a strong typed approach. It is a hack necessary
*because* subprograms in Ada have no explicit types.

If they had:

   type procedure Differentiable (X : Float) return Float;
   type procedure Non_Differentiable (X : Float) return Float;

   Sine_Waveform : Differentiable; -- Sine is differentiable
   Square_Waveform : Non_Differentiable; -- Squares are non-differentiable

   procedure Differentiate (F : Differentiable);
      -- You cannot pass squares here

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de